In recent years, diversification of utilization forms of portable electronic devices has been progressing. Portable electronic devices are required to have many performance features such as voice service, e-mail, Web access, games, and TV reception while also being small and thin so as to allow use without impairing the portability. On the other hand, the usage environment of such portable electronic devices is also becoming diversified. For example, in damp environments such as in the rain and in the kitchen, and also in the bath and poolside, a high waterproof performance is required in order to allow use without malfunctioning.
As a general method of imparting a waterproof performance to a portable electronic device, a method is widely known that, in a device housing that includes at least of pair of casings, interposes a sealing material such as rubber or an elastomer at the abutting ends portion of the casings, and fills the gaps between the casings of the device housing by the repulsion force that occurs by compressing the casings with a pressing force.
For example, the technologies shown in Patent Document 1 and Patent Document 2 are disclosed as waterproof structures that do not use a sealing member.
In the portable electronic device that is shown in Patent Document 1, a waterproof structure is provided in which, in an exterior finish body having a split structure that includes an upper case member and a lower case member, the gap at the split portion between the upper case member and the lower case member increases from the inner side of the case member to the outer side. With this kind of waterproof structure, at the gap of the coupling portion of the upper case member and the lower case member, the dimension of the outside opening portion is set to be larger than the dimension of the inside opening portion. As a result, the water drop retention force at the outside opening portion is lower than the water drop retention force of the inside opening portion, and so water drops that have entered the gap are prevented from infiltrating into the inside.
In the waterproof container that is shown in Patent Document 2, a waterproof structure is provided in which two members that constitute a housing are abutted in a stepped shape having a fixed clearance therebetween, and a water-repellent film is formed on the abutting end faces of both members. Thus, the infiltration of water drops into the housing is prevented by the water-repellent film that is provided on the abutting end faces of both members.